1. Field of the Invention
This invention relates generally to lube oil dispersant borating agents, and more particularly, to superborated succinimides and a method for production thereof. The use of the superborated succinimide of the present invention as a borating agent for nitrogen containing lube oil dispersants results in improved lubricating additive compositions in which the known tendency to degrade engine seals made from fluorine-substituted elastomers is substantially reduced.
2. Background Discussion
It is known, as illustrated by U.S. Pat. No. 3,338,834, that alkyl succinic anhydride can be reacted with tertiary-alkyl primary amines to form a monosuccinimide which can be combined with a boron containing reagent (via a boric acid-amine reaction product in this patent) to provide an additive which is useful in ashless detergent additives in lubricating oils. The alkyl succinimides are prepared by reacting alkyl-succinic anhydride with a polyamine, typically tetraethylene pentamine, in equimolar proportions to produce a monosuccinimide.
It is also known from U.S. Pat. Nos. 3,385,791, 3,703,536 and 3,718,663 that di(alkyl succinimides) of N.sub.1,N.sub.3 -symmetrical bis (aminopolyazalkylene) ureas of the formula: ##STR1## wherein k is an integer of about 2 to about 10, R.sup.2 is hydrogen or a lower alkyl group having one to four carbon atoms, R.sup.1 is an alkyl group containing from 30 to 20,000 carbon atoms, and Z is oxygen or sulfur, may be prepared by condensing an alpha, omega aminopolyazalkylene compound with urea or thiourea and then reacting the condensation product with a light oil solution of an alkyl substituted succinic anhydride in an amount to provide 2 moles of the alkyl substituted succinic anhydride product. The '536 and '663 patents disclose that the di(alkyl succinimides) of the above formula may be borated or "superborated" with aqueous boric acid to produce a product which is useful as an ashless dispersant-detergent boration agent for lubricating oils. The temperature of the borating or super-borating reaction is between about 180.degree. and 220.degree. F. (82.degree. and 104.degree. C.).
While the use of ashless dispersants in lubricants has long been known to maintain engine cleanliness, boron has also been incorporated to inhibit corrosion on copper-lead bearings in the ASTM L-38 engine test, to reduce wear in the ASTM Sequence V engine test, and to reduce the well known tendency of nitrogen containing dispersants to degrade fluorine based elastomeric engine seals (see e.g. U.S. Pat. No. 4,873,009) The present invention stems from our discovery that the source of the boron and its means of incorporation can have an effect upon the passivation of dispersant-containing lubricants toward the degradation of seals made from fluorine-substituted elastomers, and that the superborated succinimides of this invention are uniquely superior as borating agents for that purpose.